The present invention relates to a liquid dispensing, vapor controlling system. More particularly, the present invention relates to an improvement in such a system for sensing and responding (1) to the flow of liquid in the vapor passageway thereof, and (2) to the existance of an abnormal pressure in a liquid receiver with which the system is utilized.
In a variety of industries, volatile liquids are stored in bulk and dispensed in small, metered quantities to liquid receivers. For example, in the industry of servicing hydrocarbon burning vehicles, e.g., automobiles, liquid hydrocarbon fuel, e.g., gasoline, is often stored at service facilities in underground storage tanks and intermittently dispensed to the fuel tanks of the vehicles in metered quantities. To contain the hazardous vapors displaced from a liquid receiver during such a liquid dispensing operation, and prevent overfilling of the liquid receiver, a variety of liquid dispensing, vapor controlling systems have been disclosed. In the vehicle service industry, such systems typically include a nozzle having a spout, a vapor recovery means mounted on the nozzle about the spout, a vapor passageway open to the vapor recovery means, and an overfill sensor on the tip of the spout. Ideally, vapors are collected in the vapor recovery means and passed through the vapor passageway while fuel is dispensed out the spout, and the overfill sensor triggers termination of the fuel dispensing operation whenever the fuel tank is full. However, because of styling considerations, space limitations and the like, some automobiles have been produced which have fuel tank fillpipes so located and oriented that fuel cannot be dispensed into the fuel tanks thereof without overflow and overfill not sensed by a conventional overfill sensor. Consequently, a quantity of fuel may circulate through the vapor recovery means and the vapor passageway during the dispensing of fuel to such a vehicle. As a result of this circulation, the meter reading of the quantity of fuel dispensed to the automobile may be inaccurate, and liquid fuel may block the vapor passageway. If the vapor passageway does become blocked, the fuel tank may be pressurized beyond a safe, maximum limit.